Transactions of The Royal Society of Tropical Medicine and Hygiene

BackgroundMass drug administration (MDA) is the cornerstone for the elimination of lymphatic filariasis (LF). The proportion of the population that is never treated (NT) is a crucial determinant of whether this goal is achieved within reasonable timeframes. MethodsUsing two individual-based stochastic LF transmission models, we assess the maximum permissible level of NT for which the 1% mf prevalence threshold can be achieved (with 90% probability) within 10 years under different scenarios of annual MDA coverage, drug combination and transmission setting. ResultsFor Anopheles-transmission settings, we find that treating 80% of the eligible population annually with ivermectin+albendazole (IA) can achieve the 1% mf prevalence threshold within 10 years of annual treatment when baseline mf prevalence is 10%, as long as NT <10%. Higher proportions of NT are acceptable when more efficacious treatment regimens are used. For Culex-transmission settings with a low (5%) baseline mf prevalence and Diethylcarbamazine+Albendazole (DA) or Ivermectin+Diethylcarbamazine+Albendazole (IDA) treatment, elimination can be reached if treatment coverage among eligibles is 80% or higher. For 10% baseline mf prevalence, the target can be achieved when the annual coverage is 80% and NT [&le;]15%. Higher infection prevalence or levels of NT would make achieving the target more difficult. ConclusionsThe proportion of people never treated in MDA programmes for LF can strongly influence the achievement of elimination and the impact of NT is greater in high transmission areas. This study provides a starting point for further development of criteria for the evaluation of NT.

BackgroundStrongyloidiasis, caused by the parasitic intestinal worm Strongyloides stercoralis, infects hundreds of millions of people globally. Current school-based preventive chemotherapy (PC) programs that use benzimidazole derivatives (e.g., albendazole) against soil-transmitted helminths do not effectively treat strongyloidiasis, which requires treatment with ivermectin. We estimate the cost-effectiveness of mass drug administration with ivermectin for the control of strongyloidiasis. MethodsWe developed a mathematical model to simulate the population dynamics of S. stercoralis and the impact of school-based and community-wide PC across a range of epidemiological settings. We simulated 10-year PC programs with varying treatment coverages. We estimated a primary outcome of disability-adjusted life years (DALYs) averted by each PC strategy and calculate the programmatic cost (US$) of each strategy. We estimated cost-effectiveness by comparing strategies by their incremental cost-effectiveness ratios (US$/averted DALY) and expected loss curves. FindingsThe model found community-based PC was the most cost-effective strategy ([&le;]600 US$ / DALY averted), despite costing approximately 5 times as much as school-based PC. Community-based PC targeted at ages 5 and above reduced infection levels close to 0% within 5 to 6 years. School-based PC was predicted to have very little impact. These results were robust across a range of epidemiologic settings above a measured prevalence of 2-5% in school age children. InterpretationAnnual community-based PC is the most cost-effective public health strategy to control strongyloidiasis, being superior to school-based PC due to most of the infections and mortality occurring in adults. A baseline prevalence of 2% of infection in school age children, as measured by Baermann or stool culture, is a suitable minimum threshold for cost-effective implementation of community-based PC. FundingWorld Health Organization.

Mass drug administration (MDA) of antifilarial drugs is the main strategy towards the elimination of lymphatic filariasis (LF). Recent clinical trials indicated that the triple drug therapy with ivermectin, diethylcarbamazine and albendazole (IDA) is much more effective against LF than the widely used two-drug combinations (albendazole plus either ivermectin or diethylcarbamazine). For IDA-based MDA, the stop-MDA decision is taken based on microfilariae (mf) prevalence in adults. In this study, we assess how the probability of eventually reaching elimination of transmission depends on the critical threshold used in transmission assessment surveys (TAS-es) to define whether transmission was successfully suppressed and triple-drug MDA can be stopped. This analysis focuses on treatment-naive Indian settings. We do this for a range of epidemiological and programmatic contexts, using the established LYMFASIM model for transmission and control of LF. Based on our simulations, a single TAS one year after the last MDA round provides limited predictive value of having achieved suppressed transmission, while a higher MDA coverage increases elimination probability, thus leading to a higher predictive value. Every additional TAS, conditional on previous TAS-es being passed with the same threshold, further improves predictive value for low values of stop-MDA thresholds. An mf prevalence threshold of 0.5% corresponding to TAS-3 results in [&ge;]95% predictive value even when the MDA coverage is relatively low.

BackgroundThe 2030 target for schistosomiasis is elimination as a public health problem (EPHP), achieved when the prevalence of heavy intensity infection among school-aged children (SAC) reduces to <1%. To achieve this, the new World Health Organization (WHO) guidelines recommend a broader target of population to include pre-school (pre-SAC) and adults. However, the probability of achieving EPHP should be expected to depend on patterns in repeated uptake of mass drug administration (MDA) by individuals. MethodsWe employed two individual-based stochastic models to evaluate the impact of school-based and community-wide treatment and calculated the number of rounds required to achieve EPHP for Schistosoma. mansoni by considering various levels of the population never treated (NT). We also considered two age intensity profiles, corresponding to a low and high burden of infection in adults. ResultsThe number of rounds needed to achieve this target depends on the baseline prevalence and the coverage used. For low and moderate transmission areas, EPHP can be achieved within seven years if NT [&le;]10% and NT <5%, respectively. In high transmission areas, community wide treatment with NT<1% is required to achieve EPHP. ConclusionsThe higher the intensity of transmission, and the lower the treatment coverage, the lower the acceptable value of NT becomes. Using more efficacious treatment regimens would permit NT values to be marginally higher. A balance between target treatment coverage and NT values may be an adequate treatment strategy depending on the epidemiological setting, but striving to increase coverage and/or minimise NT can shorten programme duration.

BackgroundPreventive chemotherapy targeting school-aged children has substantially reduced schistosomiasis morbidity, however, a key strategic tension remains between sustaining morbidity control and pursuing transmission elimination, particularly in settings characterised by heterogeneous transmission dynamics and persistent adult infection reservoirs. We developed a health system-integrated transmission and economic evaluation framework to identify optimal age-targeting and district-level prioritisation, providing a basis for determining when elimination-focused approaches offer advantages over morbidity reduction alone. MethodsThe Thanzi la Onse individual-based model was used to evaluate alternative age-targeted mass drug administration (MDA) strategies for Schistosoma haematobium and Schistosoma mansoni across all 32 districts of Malawi from 2024-2050. Strategies included treatment of school-aged children (MDA-SAC), pre-school and school-aged children (MDA-PSAC+SAC), and community-wide treatment (all ages). Health outcomes included person-years with any infection (PY), disability-adjusted life years (DALYs), probability of elimination (defined as reaching <2% prevalence of infection in all ages). The cost-effectiveness was evaluated using incremental cost-effectiveness ratios (ICERs), net health benefit (NHB), and by quantifying the maximum costs available for implementation, using a cost-effectiveness threshld for Malawi of 88 USD per DALY averted. FindingsIn the absence of MDA, the majority of the infection burden over 2024-2050 would be concentrated in adults aged 15 years and older (219.6 million person-years [PY], 95% CI 215.4-223.4), compared with 72.8 million PY (95% CI 71.5-74.3) among school-aged children (SAC) and 25.5 million PY (95% CI 25.1- 26.2) among preschool-aged children. Annual MDA-SAC would avert approximately 18.0 million DALYs (95% CI 17.6-18.4) between 2025 and 2050 and would be highly cost-effective nationally (ICER 4.76 USD/DALY, 95% CI 4.47-4.95). Across districts, ICERs were highly variable; 25 of 32 districts were cost-effective in [&ge;]90% of runs and 29 of 32 in [&ge;]50% of runs. Expanding treatment to include preschool-aged children (MDA PSAC+SAC) would produce modest additional gains (additional 44,500 DALYs averted) but with substantially higher costs (national ICER 606 USD/DALY, 95% CI 472-695), being dominated in 22 districts and cost-effective only in the high-burden Likoma district. Community-wide MDA would achieve elimination for both species in all districts by 2030 and avert a further 98,000 DALYs; nationally it would be cost-saving relative to PSAC+SAC although outcomes were heterogeneous, with this strategy being cost-saving in 11 high-prevalence districts (2023 prevalence range 13.7 - 41.5%) but dominated (in >80% of model runs) in 16 others. Threshold analyses of maximum implementation costs indicated substantial cost margins in high-burden districts, with cost-effectiveness maintained up to approximately 25-38 USD per treatment. InterpretationThe choice of schistosomiasis strategies should depend on whether programmes prioritise short-term morbidity reduction or long-term elimination, as well as the local disease burden and the prevailing cost of service delivery. Integrating district-level transmission dynamics with opportunity-cost-based economic evaluation reveals when broader coverage is justified and provides a framework for designing fiscally grounded elimination pathways in heterogeneous endemic settings.

BackgroundSickle cell disease (SCD) is a genetic blood disorder characterized by abnormal hemoglobin S, leading to various complications. This study aimed to assess the spectrum of SCD-related complications and outcomes among pediatric patients at Mbeya Zonal Referral Hospital in Tanzania. MethodsA retrospective cross-sectional study was conducted, reviewing medical records of pediatric SCD patients admitted between June 2019 and June 2023. ResultsThe study found an inpatient prevalence of 7.7% for SCD. Vaso-occlusive pain events (68%), infections (55.3%), and severe anaemia (27.7%) were the leading causes of admission. Low rates of hydroxyurea (11.4%) and penicillin V (28.3%) use was observed. The median haemoglobin level was 6.5 g/dL, indicating significant anaemia. Newly diagnosed patients (50%) had an average age of 5.12 years at diagnosis, suggesting delayed identification. The mortality rate was 3%. ConclusionThese findings highlight the need of improved early diagnosis, management strategies, and access to essential medications for pediatric SCD patients in Tanzania. Implementation of newborn screening programs and increased awareness about SCD management could significantly improve patient outcomes.

IntroductionAnaemia is a major cause of morbidity and mortality among children in sub-Saharan Africa. Anaemia has many aetiologies best addressed by different treatments, so regional studies of the aetiology of anaemia may be required. MethodsWe analysed data from Nigerias 2018 Demographic and Health Survey (DHS) to study predictors of anaemia among children ages 6-59m. We computed the fraction of anaemia at different degrees of severity attributable to malaria and sickle cell disease (SCD) using a regression model adjusting for demographic and socioeconomic risk factors. We also estimated the contribution of the risk factors to haemoglobin concentration. ResultsWe found that 63.7% (95% CI: 58.3-69.4) of semi-severe anaemia (<80 g/L) was attributable to malaria compared to 12.4% (95% CI: 11.1-13.7) of mild-to-severe (adjusted haemoglobin concentration <110 g/L) and 29.6% (95% CI: 29.6-31.8) of moderate-to-severe (<100 g/L) anaemia and that SCD contributed 0.6% (95%CI: 0.4-0.9), 1.3% (95% CI: 1.0-1.7), and 7.3% (95%CI: 5.3-9.4) mild-to-severe, moderate-to-severe, and semi-severe anaemia, respectively. Sickle trait was protective against anaemia and was associated with higher haemoglobin concentration compared to children with normal haemoglobin (HbAA) among malaria-positive but not malaria-negative children. ConclusionThis approach used offers a new tool to estimate the contribution of malaria to anaemia in many settings using widely available DHS data. The fraction of anaemia among young children in Nigeria attributable to malaria and SCD is higher at more severe levels of anaemia. Prevention of malaria and SCD and timely treatment of affected individuals would reduce cases of severe anaemia.

Between 2015 and 2025, Cambodia reported a 99.9% decline in the number of cases of malaria. To aid acceleration of elimination, the National Center for Parasitology, Entomology and Malaria Control (CNM) implemented a package of interventions known as the Last Mile (LM) elimination program. The aim of this study was to determine the impact of the LM program on case numbers and evaluate the coverage of interventions. LM was rolled out between November 2020 and December 2023 in villages reporting a locally acquired case of Plasmodium falciparum or mixed infection with P. falciparum and P. vivax and included combinations of targeted drug administration (TDA), intermittent preventative treatment for forest goers (IPTf), active fever screening (AFS), the recruitment of a village or mobile malaria worker (VMW/MMW) and the top-up of insecticide-treated bed nets (ITN) depending on the vulnerability and receptivity of the village. A total of 103 full and 82 partial villages in seven provinces were included. Two rounds of TDA were administered, with a total of 10,678 individuals (67.6%) given during the first round and 9,678 (62.3%) during the second round. Coverage varied by province with none meeting the recommended threshold of 80%. IPTf was implemented each month among 35% (n=35) of full LM villages and 56% (n=42) of partial LM villages. A total of 11.7% (n=12) of full LM villages implemented AFS consistently on a weekly basis. Controlled interrupted time series showed no statistically significant difference in the number of malaria cases before and after the implementation of LM. Although we were unable to prove a statistically significant impact of LM, likely due to the small number of cases prior to LM, it is important to add to the limited evidence-based for Accelerator Strategies in countries approaching the elimination of malaria. Furthermore, findings from the feasibility and impact of individual interventions were used to change policy at the national level.

BackgroundSeasonal malaria chemoprevention (SMC) has been implemented yearly in northern Benin since 2019 to reduce the malaria burden in children under 5 years of age. Its geographic scope was progressively extended until in 2022 two different extensions of SMC were considered: either demographic - children aged 5 to 10 in the currently targeted departments would also receive SMC, or geographic to children under 5 in new eligible departments to the south. As SMC had neither been implemented in the areas nor age groups suggested for expansion, modelling was used to compare the likely impact of both extensions. MethodsThe model OpenMalaria was calibrated to represent the history of malaria interventions and transmission risk in Benin. Currently planned future interventions and two scenarios for SMC extensions were simulated to inform where impact would be the highest. ResultsThe model predicted that between 2024 and 2026 the geographic extension of SMC would avert at least four times more severe malaria cases and five times more direct malaria deaths per targeted child than the demographic extension. However, numbers of severe cases averted per targeted child were similar between health zones eligible for geographic extension. ConclusionsThe geographic extension is more impactful and likely more cost-effective than the demographic extension, and will be implemented from 2024. Health zones were prioritised by availability of community health workers to deliver SMC. Mathematical modelling was a supportive tool to understand the relative impact of the different proposed SMC extensions and contributed to the decision-making process. Its integration significantly enhanced the utilisation of data for decision-making purposes. Rather than being used for forecasting, the model provided qualitative guidance that complemented other types of evidence.

BackgroundTuberculosis (TB) remains one of the deadliest infectious diseases globally. Despite the World Health Organizations (WHO) End TB Strategy targets for 2035, progress has been hindered by structural, financial, and implementation barriers, including recent cuts in global funding. Strategic use of mathematical modelling is useful for prioritizing high-impact interventions and optimizing limited resources. A new global TB infection transmission model was developed to address limitations in existing tools with respect to these applications. MethodsThe model includes enhanced features such as age-specific mixing, explicit representation of asymptomatic TB, stratification by drug resistance, HIV status, and new vaccine status, and inclusion of both public and private care pathways. It was calibrated to country-specific data using Bayesian adaptive Markov Chain Monte Carlo (MCMC) methods. The model was used to assess the impact of national strategic plans and the Global Plan to End TB, using a Target Population (TP) component to map interventions to WHO guidelines. ResultsModel calibration showed good agreement with historical TB data from 29 high-burden countries, with case studies for Indonesia and Nigeria presented here. In Indonesia, comprehensive implementation of Global Plan interventions - including public-private mix efforts, modern diagnostics, improved treatment for drug-resistant TB, and a post-exposure vaccine - could enable the country to achieve End TB targets by 2035. In Nigeria, implementing its National Strategic Plan could reduce TB incidence by 27% and mortality by 37% by 2030, even without a vaccine. The model highlighted the additional efforts that are needed to meet the End-TB goals. ConclusionsThe enhanced TB model provides a flexible, policy-relevant framework for assessing the epidemiological impact of TB interventions at both national and global levels. Its open-source design and alignment with WHO recommendations make it a valuable tool for guiding evidence-based investments amid tightening global health budgets.

In sub-Saharan Africa (SSA), onchocerciasis control has been implemented for many decades, beginning in 1974 under the Onchocerciasis Control Programme in West Africa (OCP) and in 1995 in Central and East Africa (plus Liberia) under the African Programme for Onchocerciasis Control (APOC). Since the establishment of the Expanded Special Project for Elimination of Neglected Tropical Diseases (ESPEN) in 2016, data on mass drug administration (MDA) with ivermectin has been centrally compiled for all endemic countries at implementation unit (IU) level, beginning in 2013. This paper presents HISTONCHO, a database collating detailed information on interventions, including vector control, from 1975 through to 2022, using the ESPEN portal (2013-2022), regional and country reports, implementation partners records, and published literature. Reconstructing such intervention histories is crucial for an understanding of their evolution, modelling their impact, and tailoring future interventions. We discuss strengths and limitations associated with the ESPEN database, and how HISTONCHO can be improved to support modelling of intervention strategies as well as onchocerciasis control and elimination efforts by endemic country programmes.

BackgroundVenezuela has experienced an explosive resurgence in Plasmodium falciparum and Plasmodium vivax malaria incidence over the last decade due to various social, political, and economic factors. To ensure national and regional progress towards malaria elimination, there is an urgent need to better understand the epidemiological dynamics of this malaria outbreak at its epicenter in the southern state of Bolivar and to identify the sets of interventions that may be necessary to reduce transmission and incidence. MethodsWe fitted transmission models of P. falciparum and P. vivax to weekly incidence data in Bolivar, Venezuela during 2000-2018. We estimated the magnitude of local transmission for both Plasmodium spp. and inferred the contribution of relapses and reinfections to P. vivax incidence in the region. Compared to a business-as-usual scenario, we projected the impact of different interventions on Plasmodium spp. incidence during the period 2021-2023. FindingsWe estimated that 63{middle dot}7 - 73{middle dot}3% of all P. vivax infections in Bolivar are relapses, leading to as many as 51,800 observed relapses misclassified per year as reinfections in the routine surveillance data. Our estimates suggest that the reproduction number remains close to one for both Plasmodium spp., pointing towards the feasibility of control. Long-lasting insecticidal nets (LLINs) were projected to cause greater proportional reductions in P. falciparum incidence than P. vivax incidence, and mass drug administration (MDA) with an 8-aminoquinoline and a blood-stage partner drug was projected to cause the greatest reduction in P. vivax incidence, provided that adherence rates were high. InterpretationControl of the malaria outbreak in Southeastern Venezuela is feasible, should appropriate resources to support surveillance and control be brought to bear. Coupling the distribution of LLINs and a focal MDA with an 8-aminoquinoline and a blood-stage partner drug may lead to the greatest reduction in malaria incidence. FundingNational Science Foundation; University of Notre Dame; National Institute of General Medical Sciences (grant number 1R35GM143029-01 to TAP); RESEARCH IN CONTEXTO_ST_ABSEvidence before the studyC_ST_ABSWe searched PubMed, bioRxiv, and medRxiv for articles in English published on or before May 25th, 2021 using the following keywords: "Venezuela", "malaria", AND "model*". Previous studies have applied statistical models to characterize the relationship between malaria incidence and climate in Venezuela, concluding that the reproduction number is low and suggesting the feasibility of control. A study fitting a mechanistic transmission model to epidemiological data to allow for projecting the impact of alternative approaches to control has not been performed. Added value of the studyWe fitted Plasmodium falciparum and Plasmodium vivax transmission models to 20 years of weekly incidence data to estimate the transmission of both Plasmodium spp. and characterize the contribution of relapses and reinfections to P. vivax incidence in Bolivar, Venezuela. We also projected the likely impact of interventions in the region under alternative scenarios about control. Implications of the available evidenceThe burden of Plasmodium vivax relapses in Bolivar is underestimated from routine surveillance data, so control interventions must target the hypnozoite reservoir in the region. Mass drug administration (MDA) is projected to be impactful for both Plasmodium spp., though tradeoffs between coverage and adherence suggest that a focal MDA with an 8-aminoquinoline and a blood-stage partner drug may yield the greatest impact.

BackgroundMalaria transmission in Uganda is heterogenous, so the national malaria program needs information about the distribution of malaria to develop appropriate policies. While population-based community surveys estimate Plasmodium falciparum parasite rate (PfPR), they are too infrequent and sparse for routine malaria management. Health facility data is routinely collected and covers a large geographic scope, but the data is collected passively, variable in quality, and potentially highly biased. We aimed to triangulate test positivity rate (TPR) from health facility data to survey estimated PfPR data in Uganda to create monthly, high-resolution PfPR estimates. MethodsUsing matched health facility and survey data, we fit a multi-level logistic regression model that accounted for clustering at the district and region level, to predict PfPR from TPR. Additional covariates were explored to select a final model that reduced bias while prioritizing its utility for programmatic tasks. Model predictions were validated against observed PfPR and used to generate monthly district-level prevalence estimates from 2016 to 2024. Regional and national level estimates were made by weighting district level estimates by population. ResultsThe final model included a smoothed TPR term and proportion of severe malaria cases at a district-month level. Predicted PfPR was strongly positively correlated with the observed survey PfPR (Pearsons rank correlation rho =0.79, p<0.001). National estimates derived from predicted PfPR aligned well with survey estimates from the same time and area. ConclusionHealth Management Information System (HMIS) data, when paired with research data, can be used to estimate malaria prevalence with high spatial and temporal resolution. Estimates can be tested and models can be updated to help malaria programs best leverage facility data. In the context of declining survey frequency, HMIS-based modeling offers a resilient and cost-effective alternative for malaria surveillance and programmatic decision-making in Uganda and similar high-burden settings.

Lymphatic filariasis (LF) is a mosquito-borne neglected tropical disease (NTD) caused by filarial worms. India accounted for 55% of the global population at risk of LF in 2021. The World Health Organization (WHO) has targeted LF elimination by 2030; however, India aims to achieve LF elimination prior to the global WHO NTD target. Mathematical models are useful tools to evaluate and guide elimination strategies. We propose a new compartmental model--COmpartmental Modelling of Elimination strategies and Transmission of Lymphatic Filariasis (COMET-LF)--to assess the impact of mass drug administration (MDA) on LF elimination. Our model incorporates drug efficacy data from a clinical trial and generates estimates of disease (lymphoedema and hydrocele) prevalence. The model is calibrated to publicly available microfilaria (Mf) and disease prevalence data (2008-2013) from Bihar, India. Predictions of the number of MDA rounds needed for achieving the elimination threshold were generated for various endemic scenarios. The projected estimates were compared with established micro- (LYMFASIM) and macro- (EPIFIL) simulation models for LF transmission. Disease burden estimates and the impact of MDA on disease burden were generated using COMET-LF for different endemic scenarios. Our simulations suggest that the disease burden reduces over much longer timescales - 20 years for a reduction of 8%-11.5% following 5 rounds of MDA. We extended COMET-LF to a meta-population model to investigate the role of migration among neighbouring regions on elimination and resurgence probabilities. We found that high Mf prevalence in the spatial neighbourhood can increase the number of required MDA rounds for elimination up to 3 additional rounds for the two-drug regimen. Furthermore, we assess the impact of migration on the resurgence probability in a non-endemic region which is spatially adjacent to a high-Mf prevalence region and show that there is a significant risk of resurgence if Mf prevalence exceeds 5%. Our model can be easily tailored to specific blocks and districts to guide programmatic intervention for disease management and LF elimination. Author summaryLymphatic filariasis (LF) commonly occurs in tropical regions and is transmitted to humans by mosquitoes infected with larvae of parasitic roundworms. Some patients develop external symptoms including swollen limbs/male genitals that develop from damage to lymph nodes. Others do not develop external symptoms but may transmit the disease to non-infected humans through mosquito bites. LF causes physical disability, disfigurement and mental suffering. India has more than half of the global population at risk of developing LF. Currently, medications that kill the parasites are given yearly to the population at risk. A better understanding of the disease transmission and control measures is important to meet the 2030 elimination target set by the World Health Organization. We developed a new mathematical model (COMET-LF) that takes into account India-specific disease information for more accurate predictions. To validate our model, we compared the predictions with those from established models. COMET-LF can predict the number of years the drug has to be administered to stop LF transmission and the effect of drugs on disease prevalence. COMET-LF also shows that infected patients migrating from neighboring regions can increase transmission to regions where LF is under control. Notably, our model can help policy makers plan targeted control measures for specific regions.

Insecticide-treated nets (ITNs) are central to malaria prevention in sub-Saharan Africa, but their effectiveness depends on how long households retain and use them. Although ITNs are designed to last three years, recent evidence suggests median retention times are significantly shorter in most countries, creating gaps in protection between mass distribution campaigns. In this study, we model the potential impact of improving ITN retention by enhancing physical durability on malaria burden across 43 countries in sub-Saharan Africa using an individual-based malaria transmission model. We simulate scenarios in which ITN retention times are extended by 1 to 8 months beyond current country-specific baselines and compare averted cases relative to a business-as-usual scenario. Results show that a 4-month increase in retention could avert 6% of malaria cases over three years; and that to get the same amount of impact from increasing ITN access would require an additional 171 million nets. Gains from improved retention are greatest in the first few months of extension and accumulate over time, making durability enhancements a cost-effective strategy for maintaining protection as funding constraints grow. These findings support the integration of predictive durability metrics, such as the Resistance to Damage (RD) score, into ITN procurement decisions and highlights the importance of selecting well performing, high-value ITNs to strengthen malaria control without deploying more ITNs.

BackgroundSchistosomiasis remains a major public health challenge in sub-Saharan Africa. Recent World Health Organization (WHO) guidance calls for community-wide treatment and fine-scale data to optimise preventive chemotherapy (PC) strategies, yet the practical implications for resource allocation by health ministries are unclear. MethodsWe analysed epidemiological and cost data from Ethiopia and Zimbabwe to compare survey designs and five implementation scenarios. Scenarios varied by data source, administrative unit of implementation, WHO guidance on PC strategies. Outcomes were target population, praziquantel needs, and delivery costs. ResultsGeostatistical surveys reduced sample size by up to 90% and survey costs by [&ge;]72% compared with a design-based approach, while increasing spatial coverage. Applying updated WHO guidance expanded eligibility to pre-school-aged children and adults, and in one scenario increased treatment needs by 72% in Ethiopia and 262% in Zimbabwe. Correspondingly, praziquantel requirements and delivery costs were driven primarily by expanded age eligibility rather than geographic coverage. ConclusionsGeostatistical surveys provide substantial efficiency gains for impact assessments, enabling cost-efficient, granular targeting. However, implementing 2022 WHO guidance was the dominant driver of increases in programme scope and resource needs, underscoring the importance of accurate fine-scale data to guide efficient planning and budgeting toward elimination goals. Author summarySchistosomiasis control programmes are required to use finer-scale data and updated World Health Organization (WHO) guidance to decide where and how often to deliver praziquantel. We analysed national schistosomiasis data and programme costs from Ethiopia and Zimbabwe to compare different approaches to impact assessment surveys and to estimate how treatment needs change under alternative decision rules.We found that model-based geostatistical surveys can reduce the number of people that need to be sampled and the cost of surveys while providing more detailed information for planning at sub-district level. However, when we applied the 2022 WHO schistosomiasis guidance, expanded eligibility (including adults and pre-school-age children and a lower threshold for community-wide treatment) substantially increased the number of people needing treatment. In our scenarios, expanded eligibility drove much larger increases in praziquantel requirements and delivery costs than changes in geographic coverage. Our findings help health ministries to anticipate the operational and budget implications of updated guidance and highlight why accurate fine-scale data are essential for equitable and realistic planning toward elimination.

BackgroundMalaria elimination in mobile and hard-to-reach populations calls for new, tailored interventions. In the Guiana Shield countries, the malaria burden is high in the population working in illegal gold mining. Between April 2018 and March 2020, we implemented Malakit, a new intervention targeting gold miners, and relying on the distribution of kits for self-diagnosis and self-treatment. In this study, we evaluate the impact of Malakit on malaria transmission. MethodsWe fitted a mathematical model of malaria transmission to surveillance data from Brazil and Suriname, and to prevalence data from cross-sectional surveys, to estimate the change in treatment coverage and reproduction number between the pre-intervention (2014-2018) and intervention (2018-2020) periods. ResultsModel results show that treatment coverage of symptomatic all-species malaria infections increased from 26.4% (95%CrI 22.8, 30.3) prior intervention to 55.1% (95%CrI 49.9, 60.8) during the intervention, leading to a decrease of the reproduction number from 1.19 to 0.86. We estimate that on average 6943 all-species malaria infections were averted during the intervention, corresponding to a 48.7% reduction in incidence and 43.9% reduction in total infection prevalence. DiscussionMalakit had a significant impact on malaria transmission by improving the access to treatment of the population working in illegal gold mining in French Guiana. Building on the regional efforts of the past twenty years, Malakit contributed to another step towards malaria elimination in the Guiana Shield.

BackgroundSchistosomiasis affects over 200 million people and causes significant urogenital and gastrointestinal morbidity. Mass drug administration (MDA) with praziquantel is used to mitigate severe illness and reduce infection rates. Portable microscopy, combined with artificial intelligence (AI), offers a novel method for schistosomiasis screening in low-resource settings. This study tested whether re-training AI models for Schistosoma egg detection with local field data, a process we call "edge-tuning", could improve the models performance on the following field day. MethodsThis study in Cote dIvoire evaluated a portable microscope (NTDscope) for Schistosoma haematobium screening. Urine samples from 100 community members were analyzed using AI models on the NTDscope and traditional light microscopy. Starting AI models, trained on images from a previous version of the NTDscope, were edge-tuned after the first day of sample collection using cloud-based image annotation and re-training. Starting and edge-tuned models were evaluated at confidence thresholds optimizing for sensitivity, specificity, or egg counting. FindingsFor all thresholds, edge-tuned models performed better than starting AI models. Compared to manual counting of eggs on the NTDscope, sensitivity of the starting AI model on day 2 ranged from 59.3%-75.5%, with specificity ranging from 46.7%-85.7%. After edge-tuning, sensitivity increased to 77.8%-100%, with specificity from 78.6%-100%. Compared to light microscopy, edge-tuned AI models had comparable performance to manual counting from NTDscope images. InterpretationPortable microscopy is an effective solution for rapid, on-site schistosomiasis screening. AI- based egg detection increases diagnostic throughput while maintaining good performance. This study demonstrates that edge-tuning AI models with local data significantly improves their performance and can be performed in low-resource settings, making the combined technologies effective tools for monitoring schistosomiasis programs in endemic areas.

Background: The World Health Organization proposes that elimination of onchocerciasis transmission (EOT) be verified in 12 endemic countries by 2030. In sub-Saharan Africa (SSA), where most cases occur, Niger is the only country that has been verified to date. Despite decades of ivermectin mass drug administration (MDA), infection persists in West and Central Africa. Alternative treatment strategies (ATS) are necessary to accelerate progress towards EOT by 2030 and beyond. Methods: We used the EPIONCHO-IBM transmission model to project the number of years, from 2026, to reduce microfilarial (mf) prevalence below 1% across 1,634 implementation units (IUs) in 19 SSA countries. We fitted the model to geostatistically-derived mf prevalence in 1975, 2000 and 2018, and projected mf prevalence through to 2025. We classified IUs according to their baseline endemicity, intervention history programmatic performance, and current (2025) MDA frequency (annual or biannual). For those IUs that would not reach < 1% mf prevalence by 2030 if current strategies were continued, we simulated ATS (increasing treatment frequency, improving coverage, and adopting moxidectin MDA) from 2026 to 2040. Results: Of the 1,486 IUs currently under annual ivermectin MDA, 45% would require ATS. In those low-moderate endemicity IUs, biannual ivermectin would have a comparable impact to that of switching to annual moxidectin; in those with high endemicity, adopting biannual moxidectin would be more impactful. Of the 148 IUs currently receiving biannual ivermectin, 24% would benefit from ATS, switching to biannual moxidectin being the best option. Conclusion: This work brings into sharper focus which IU profiles are most likely to require ATS across SSA. In highly-endemic IUs with long intervention histories, biannual moxidectin MDA may be required under our modelling assumptions, with substantial uncertainty surrounding the permanent sterilising effect, of the two drugs under comparison, upon adult female worms. National programmes aiming to reach EOT will have options that need to be balanced against financial considerations. Implementation studies will also be important for translating these modelling projections into national policy decisions, particularly where different intervention strategies generate similar epidemiological benefits. Economic and epidemiological evaluations of repeated moxidectin MDA are needed to inform these decisions.

There is an urgent need to maximize the effectiveness of existing malaria interventions and optimize the deployment of novel countermeasures. When assessing the effects of interventions against malaria, it is imperative to consider the interdependence of people and the resulting indirect effects, without which the impact on health outcomes and their cost-effectiveness may be miscalculated. Here, we conducted a scoping review of existing literature on the indirect effects of malaria interventions. We observed a recent increase in both the number of reports and the variety of terms used to denote indirect effects. We further classified eight categories of comparative analysis to identify the indirect effects, proposed common terms for the indirect effects, and highlighted the potential benefits of mathematical models in estimating indirect effects. Improving the study design and reporting the indirect effects of malaria interventions will lead to better informed decisions by policymakers.